This invention relates to refrigeration apparatus, and more particularly, to an arrangement for dampening noise generated by the motor-compressor unit of said apparatus.
Refrigeration apparatus employed in air conditioning equipment for residential applications are generally located in areas that are either occupied, for example the well-known room air conditioners are typically mounted in windows or installed through the walls of rooms, or provided as a "split system" wherein the motor-compressor unit and condenser are mounted in a common housing and installed outdoors on a concrete slab or similar foundation. As is well recognized, it is important that such air conditioning equipment be limited generators of noise.
As is apparent, if the equipment is a noise generator, it will produce undesired disturbances in either the occupied space being served by such equipment, or if located outdoors, it may disturb not only the owner therof, but also the owner's neighbors who may reside in relatively close proximity to the air conditioning equipment.
As is well recognized, motor-compressor units of the type typically employed in air conditioning equipment of the type under discussion are one of the principal sources of noise generated by the equipment. The compressor employed to produce the high pressure refrigerant gas includes many moving components, all of which generate noise. Typically, in units of the type under discussion, the motor-compressor unit is resiliently suspended in a hermetically sealed shell. In order to reduce manufacturing costs, the size of the shell has been continually decreased whereby a substantial portion of the compressor unit is disposed in the oil sump defined by the interior surface of the shell. It has been found that the lubricating oil acts as a conduit for sound generated by the motor-compressor unit. In effect, such sound is transmitted by the oil to the shell from where it radiates to the surrounding ambient.
In order to reduce the transmission capability of the oil, many devices have heretofore been employed to aerate or agitate the oil. For example, in U.S. Pat. No. 2,990,111, there is disclosed a mechanical stirrer located in its entirety below the surface of the oil in the sump. The stirrer agitates the oil to produce bubbles therein to reduce the oil's transmission capability. In U.S. Pat. No. 3,066,857, a portion of the compressed gas is bypassed about the piston and is delivered to the lubricating oil through a suitable passage. The high pressure refrigerant gas causes the oil to foam or bubble to thereby reduce its noise transmitting capabilities. Another example of the prior art is disclosed in U.S. Pat. No. 3,147,914 wherein the rotor of the motor is submerged in the oil and agitates the oil as the rotor rotates. The several examples cited above all have a common feature. Each of the patents of the prior art agitate the oil to produce bubbles in the oil which tend to reduce the oil's noise transmission capability. However, none of the devices of the prior art are entirely satisfactory for one or more reasons.
For example, it has been found that by agitating or stirring the oil in the manner disclosed in U.S. Pat. No. 2,990,111, particles of debris usually found at the bottom of the oil sump are stirred about and sometimes find their way into the lubricating pump's inlet. This results in the particles being delivered to the various bearings of the unit to thereby reduce bearing life.
With reference to the device disclosed in U.S. Pat. No. 3,066,857, it has been found that the bubbles will be insufficiently distributed throughout the entire body of oil by merely causing refrigerant gas to bypass the piston. In addition, since the quantity of bypass gas is not constant due to manufacturing tolerances, sufficient quantities of bubbles are not always formed in the oil.